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Life from Earth, elsewhere

A color-enhanced scanning electron micrograph of a waterbear, an extremophile that has been known to survive in space.

In class, we have discussed the possibility that life on Earth did not originate on Earth, but came to Earth on an asteroid or other impactor. But another idea is that the inverse is true: Later impacts on Earth sent life to other locations in the Solar System. Recent simulations suggest that some of the known or believed impacts Earth has sustained were large enough to send some debris to Mars, Jupiter, and possibly even Saturn. We know that Mars may have once been habitable, and we suspect that one or more of Jupiter’s moons are habitable—so is it possible that some extremophiles, such as waterbears, were included in the debris that got sent to other worlds and started life there? Some scientists think so.